<template>
    <div class="selection-component">
        <div class="selection-show"  @click="toggleDrop">
            <span>{{selections[nowIndex].label}}</span>
            <div class="arrow"></div>
        </div>
        <div class="selection-list" v-if="isDrop">
            <ul>
                <li v-for="(item, index) in selections" @click="chooseSelection(index)">{{item.label}}</li>
            </ul>
        </div>
    </div>
</template>

<script>
    export default {
    props:{
        selections:{
            type:Array,
            default:[{
                label:'test',
                value:0
            }]
        }
    },
    data(){
       return {
        //选择一个变量来控制list的显示
        isDrop:false,
        nowIndex:0
    }
    },
    methods:{
        toggleDrop () {
            this.isDrop = !this.isDrop;
        },
        chooseSelection(index){
            this.nowIndex=index
            this.isDrop = false
            this.$emit('on-change',this.selections[this.nowIndex])
        }
    }
    };
</script>

<style>
.selection-component {
  position: relative;
  display: inline-block;
}
.selection-show {
  border: 1px solid #e3e3e3;
  /* 只设置padding,宽度由文字决定 */
  padding: 0 20px 0 10px;
  display: inline-block;
  position: relative;
  cursor: pointer;
  height: 25px;
  line-height: 25px;
  border-radius: 3px;
  background: #fff;
}
.selection-show .arrow {
  display: inline-block;
  border-left: 4px solid transparent;
  border-right: 4px solid transparent;
  border-top: 5px solid #e3e3e3;
  width: 0;
  height: 0;
  margin-top: -1px;
  margin-left: 6px;
  margin-right: -14px;
  vertical-align: middle;
}
.selection-list {
  display: inline-block;
  position: absolute;
  left: 0;
  top: 25px;
  width: 100%;
  background: #fff;
  border-top: 1px solid #e3e3e3;
  border-bottom: 1px solid #e3e3e3;
  z-index: 5;
}
.selection-list li {
  padding: 5px 15px 5px 10px;
  border-left: 1px solid #e3e3e3;
  border-right: 1px solid #e3e3e3;
  cursor: pointer;
  background: #fff;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.selection-list li:hover {
  background: #e3e3e3;
}
</style>